The present invention relates to a material for packaging light-sensitive materials, in particular, to a material for packaging light-sensitive materials, having improved flexibility, tear strength and heat-seal properties.
Packaging materials completely intercepting light are used for packaging light-sensitive materials which will cause their quality and value to deteriorate on exposure to light. Such packaging materials must have excellent light-shielding properties; physical strengths such as breaking strength, tear strength, extent of impact perforation, Gelbo test strength etc.; heat seal properties such as heat seal strength and hot seal strength; anti-static properties and the like. It is difficult to provide a single film material which possesses all the above-mentioned properties. Therefore, composite laminated films composed of an LDPE film comprising carbon black or pigments dispersed therein, and flexible sheets such as paper, aluminum foil, cellophane etc. have heretofore been used in the art.
Such laminated films do not have sufficient physical properties and have disadvantages in that they are readily torn or pinholed during packaging work and in that heat sealed portions are readily separable. Furthermore, incorporation of a great quantity of light intercepting material (referred to "light-shielding material" hereinafter) such as carbon black urges to reduce the physical strengths to a great extent. Thus the amount of the light-shielding material should be limited to about 3 weight % and the thickness of film should be not less than 70 .mu.m resulting in that the film becomes so bulky and rigid as to entail a poor processing properties on packaging and a high manufacturing cost.